The Indian Ocean, with its crowded and in some cases contested sea lanes, is becoming the center of international maritime rivalry, with various powers jousting for influence and advantage in the world's third largest body of water, which serves as a vital transit route for the global economy.

As if to highlight this trend, the Chinese navy recently conducted live-fire drills in the western Indian Ocean. China's state-run Xinhua News Agency quoted the fleet commander as saying that his ships "carried out strikes against 'enemy' surface ships" in an "exercise that lasted several days." The fleet included a destroyer, a guided-missile frigate and a supply vessel. Earlier this year, similar live-fire drills were carried out in the eastern Indian Ocean by a Chinese fleet that also included a destroyer.

As the Chinese live-fire exercises show, the geostrategic maritime environment in the Indian Ocean is altering fundamentally. After consolidating its position in the South China Sea, Beijing is focusing increasingly on the Indian Ocean. A 1971 United Nations resolution declaring it a "zone of peace" has fallen by the wayside.

China's increasing activity reflects a strategic shift from "offshore waters defense" to "open seas protection," in the name of safeguarding its trade and energy interests. This mirrors the evolution of its land-combat strategy from "deep defense" (luring enemy forces into Chinese territory, where they can be garroted) to "active defense" (a proactive posture designed to fight on enemy territory).

Beijing is also employing supposedly economic initiatives to advance its geostrategic ambitions, including implementing its Maritime Silk Road project to gain a major foothold in the Indian Ocean and chip away at India's natural-geographic advantage.

In recognition of this changing situation, U.S. Defense Secretary Jim Mattis kicked off a visit to New Delhi on Sept. 26 by offering a slew of weapon systems to India, including 22 unarmed MQ-9 "Reaper" unmanned aerial vehicles to aid naval intelligence, surveillance, reconnaissance and precision strikes. Mattis's boss, President Donald Trump, recently called India "a key security and economic partner of the United States" and said the two countries are "committed to pursuing our shared objectives" in the Indo-Pacific region.

The growing importance of the Indian Ocean resources and sea lanes is apparent. More than half of the world's container traffic, two-thirds of its seaborne petroleum trade, and a third of all maritime traffic traverse the ocean, much of it through chokepoints such as the Malacca and Hormuz straits.

The Indian Ocean is also rich in mineral wealth, with deep seabed mining emerging as a major new strategic issue. Various powers are seeking to tap seabed resources extending from sulfide deposits -- which contain valuable metals such as silver, gold, copper, manganese, cobalt and zinc -- to phosphorus nodules for phosphor-based fertilizers, underscoring the need for a regulatory regime and environmental protection.

The dangerous rush to exploit mineral and halieutic resources threatens to impose considerable environmental costs and spark new conflicts and confrontations. For example, several studies have indicated that commercial fishing by foreign fleets, by depleting local resources, has driven poor Somali fishermen to piracy.

Projecting naval power

The growth of nonstate actors such as pirates, terrorists and criminal syndicates off the Horn of Africa and elsewhere is also linked with the increasing density and importance of maritime flows through the Indian Ocean. This development, however, has become a pretext for outside powers to intervene and to project naval power. China, for example, has used the excuse of oceanic piracy to launch naval operations around the Horn of Africa and to set up its first overseas naval base at Djibouti, at the northwestern edge of the Indian Ocean in north Africa.

China's growing activities in the Indian Ocean draw strength from its success in changing the status quo in its favor in the adjacent South China Sea, where it has pushed its borders far out into international waters in a way that no power has done elsewhere. By erecting military facilities on manmade islands in the Spratly and Paracel archipelagos, China has positioned naval and air power at the mouth of the Indian Ocean.

It is now rapidly expanding its Indian Ocean footprint after setting up the Djibouti base and investing in building regional ports, including in Pakistan at Gwadar (which sits strategically at the mouth of the Strait of Hormuz), in Sri Lanka at Hambantota, and in Myanmar at Kyaukpyu. It also has port projects in the Seychelles and the Maldives. China's submarine fleet -- one of the fastest-growing in the world -- is best suited not for the shallow South China Sea but for the Indian Ocean's deep waters, a message Beijing has conveyed by dispatching attack submarines to the area.

It was always clear that if China got its way in the South China Sea, it would turn its attention to the Indian Ocean and the western Pacific. Yet U.S. President Barack Obama's administration allowed China to change the status quo by force in the South China Sea without incurring any international costs, even though this development carries greater and more far-reaching international geopolitical ramifications than Russia's actions in Ukraine. Under Trump, the U.S. has shown no desire to seek a return to the status quo ante in the South China Sea. As a result, China is firming up its dominance there, while the U.S. symbolically undertakes freedom-of-navigation operations.

Cost-free unilateralism

In effect, China has demonstrated that defiant unilateralism is cost-free. This has left countries bearing the brunt of China's recidivist policies with difficult choices. However, China's actions have prompted Japan to reverse a decade of declining military outlays and India to revive stalled naval modernization.

Japan, which is heavily dependent on the Indian Ocean region for supplies of energy and raw materials, has also stepped up its regional engagement. For example, it is investing in eight port construction or renovation projects in Indonesia, India, Iran, Oman, Kenya, Mozambique, Madagascar and the Seychelles. Japan is also seeking to play a more active role in protecting the Indian Ocean sea lanes.

India, despite its strategic depth in the Indian Ocean, faces a new threat from the oceanic south. With Chinese submarines now making regular forays into India's maritime backyard right under the nose of its Andaman and Nicobar Command, New Delhi must devise concrete steps to deal with China's growing footprint.

With India's energy and strategic infrastructure concentrated along a vulnerable, 7,600km coastline, the emergence of an oceanic challenge represents a tectonic shift in the country's threat calculus. Yet it has been slow to face up to this reality. It needs a comprehensive maritime security strategy backed by naval capabilities that can take on tasks ranging from protecting and securing the seas to projecting power across the Indian Ocean region.

The Andaman and Nicobar archipelago in the Bay of Bengal is a critical asset for India to counter the growing Chinese maritime presence and to blunt the increasing land-based, trans-Himalayan military threat mounted by China. Located next to the Strait of Malacca, the Andaman and Nicobar chain offers control of this strategic chokepoint, which is one of China's greatest maritime vulnerabilities. Just as the Chinese military harasses and threatens Indian border patrols in the Himalayas, India can potentially play the same game off the Andaman and Nicobar chain, including by establishing China-style civilian maritime militias backed by the Indian Coast Guard.

The importance of this chokepoint can be easily stated: A third of the 61% of global petroleum and other liquids production that moves on maritime routes transits the Strait of Malacca, including around 82% of China's fuel imports. China's hold on the South China Sea jugular makes the Strait of Malacca chokepoint a critical defense area for Indian security.

More fundamentally, greater maritime cooperation among democratic powers is becoming inescapable. Cooperation between Japan, India, Australia, Indonesia and the U.S. must extend to guarding the various "gates" to the Indian Ocean by exerting naval power at critical chokepoints. The aim should be to forestall the emergence of a destabilizing Sinocentric Asia. The common observation that, "Whoever controls the Indian Ocean dominates Asia," is unattributed, but nonetheless true.